The desired properties of printing inks vary with the type of ink. Flexographic and gravure inks, for example, must have gloss, adhesion to the substrate, and resistance to heat and scuffing. Heatset lithographic inks should be resistant to rubbing and scuffing. Publication gravure inks must have high gloss and scuff resistance. Water-based inks and photocurable inks also have specific needs.
Attempts are being made to develop resins that would impart to these inks the required properties. Conventional water-soluble rosin-modified maleic acid resins are commercially utilized, but they give brittle films that lack scuff resistance. Copolymers of styrene and maleic anhydride are also used, but they lack adequate adhesion to many packaging films. Conventional polamide resins have generally good overall properties, but they lack heat resistance in packaging inks and show inadequate adhesion to many polypropylene films that are growing in importance as packaging materials.